P-118: Effect of Vitrification on Developmental Competence of Parthenogenetic Activation in In Vitro Matured Ovine Oocytes

Background: Cryopreservation of in vitro matured oocytes is a useful technique because the oocytes can be used for some assisted reproductive technologies. On the other hand, the cryopreservation of oocytes is an open problem as a result of their structural sensitivity to the freezing process. The purpose of this study was to evaluate the effect of vitrification on in vitro development of vitrified in vitro matured ovine oocytes after chemical activation. Materials and Methods: Immature oocytes were collected from abattoir-derived ovaries, matured in vitro. Then, in vitro matured oocytes divided into two groups: 1. vitrified in cryotop (VTR); 2. without treatment as a control (CTR). 407 matured ovine oocytes were cryopreserved by vitrification. oocytes were exposed to 7.5% EG + 7.5% DMSO for 3 minutes and then 15% EG + 15% DMSO + 0.5 M sucrose for 25 seconds, loaded in cryotops and immersed into liquid nitrogen. After warming, oocytes were cultured in vitro for 30 minutes and then parthenogenically activated using ionomycin for 1 minute and subsequently incubated in 6-dimethylaminopurine (6-DMAP) for 2 hours. Results: When vitrified-warmed oocytes were activated, blastocyst rates in VTR (10.21%) group was significantly lower (p< 0.05) than in CTR (39.50%). Conclusion: Vitrification procedures effect on the structural components and biochemical and molecular events such as spontaneous parthenogenetic activation that could be a reflection of injuries to cytoplasmatic biochemical components leading to abnormalities in the cell cycle control, degeneration and low developmental competence of vitrified MII ovine oocytes.